Rolling device for information apparatus

Abstract

A rolling device is made up of a plurality of rolling bodies provided between an outer member having a first contact face with each of the plurality of rolling bodies and an inner member having a second contact face with each of the plurality of rolling bodies wherein the plurality of rolling bodies individually are able to roll relative to the first and second faces. A grease composition is sealedly filled in between the outer member and the inner member and contains a carbonate compound serving as a base oil, a lithium soap serving as a thickener, and at least one organomolybdenum compound selected from the group consisting of a molybdenum dithiophosphate and a molybdenum dithiocarbamate.

What is claimed is:  
     
       1. A rolling device comprising a plurality of rolling bodies provided between an outer member having a first contact face with each of the plurality of rolling bodies and an inner member having a second contact face with each of the plurality of rolling bodies, the plurality of rolling bodies individually being able to roll relative to the first and second faces, wherein a grease composition is sealedly filled inbetween said outer member and said inner member and comprises: 
       a carbonate compound of the following general formula (i) serving as a base oil                    
       wherein R and R′ may be the same or different and independently represent a branched alkyl group having from 13 to 15 carbon atoms; 
       a lithium soap serving as a thickener; and  
       at least one organomolybdeniun compound selected from the group consisting of a molybdenum dithiophosphate of the general formula (ii)                    
       wherein R 1 , R 2 , R 3  and R 4  independently represent an alkyl group having from 1 to 24 carbon atoms or an aryl group having from 6 to 30 carbon atoms, and a molybdenum dithiocarbamate of the general formula (iii)                    
       wherein R 5 , R 6 , R 7  and R 8  independently represent an alkyl group having from 1 to 24 carbon atoms, and X represents O or S. 
     
     
       2. A device according to claim  1 , wherein said base oil is made of a carbonate compound of the following general formula (i)                    
       wherein R and R′ may be the same or different and independently represent a branched alkyl group of the following general formula (iv)                    
       wherein n=13 to 15 and m=0 to 6. 
     
     
       3. A device according to claim  1 , wherein said rolling bodies are each made of a spherical body or ball. 
     
     
       4. A device according to claim  1 , wherein the rolling bodies are each made of a cylindrical roller. 
     
     
       5. A device according to claim  1 , wherein said grease composition comprises 70 to 95 parts by weight of said carbonate compound of the general formula (i), and 5 to 30 parts by weight of said lithium soap                    
     
     
       6. A device according to claim  1 , wherein said lithium soap consists of a lithium metal salt prepared from lithium hydroxide and a higher fatty acid having not smaller than 10 carbon atoms or a higher hydroxy fatty acid having at least one hydroxyl group and not smaller than 10 carbon atoms. 
     
     
       7. A device according to claim  1 , wherein said thickening agent is made of a mixture of lithium metal salts. 
     
     
       8. A device according to claim  1 , further comprising additives as a fourth component. 
     
     
       9. A device according to claim  1 , wherein the at least one organomolybdenum compound is present in an amount of 0.5 to 5 wt % based on the grease composition. 
     
     
       10. In a rolling device used in spindle motors in an information device and comprising a plurality of rolling bodies provided between an outer member having a first face in contact with each of the plurality of rolling bodies and an inner member having a second face in contact with each of the plurality of rolling bodies, each of the plurality of rolling bodies being able to roll relative to the first and second faces, the improvement characterized in that a grease composition comprising: 
       a carbonate compound of formula (i) serving as a base oil                    
       wherein R and R′ may be the same or different and independently represent a branched alkyl group having from 13 to 15 carbon atoms; 
       a lithium soap serving as a thickener; and  
       at least one organomolybdenum compound selected from the group consisting of a molybdenum dithiophosphate of formula (ii)                    
       wherein R 1 , R 2 , R 3  and R 4  independently represent an alkyl group having from 1-24 carbon atoms or an aryl group having from 6 to 30 carbon atoms, and a molybdenum dithiocarbamate of formula (iii)                    
       wherein R 5  , R 6 , R 7  and R 8  independently represent an alkyl group having from 1 to 24 carbon atoms, and X represents O or S, is sealedly filled in between said outer member and said inner member. 
     
     
       11. A rolling device according to claim  10 , wherein said information device is selected from the group consisting of a hard disk drive, a floppy disk drive, a compact disk drive, a magneto-optical disk drive and video tape recorder. 
     
     
       12. A rolling device according to claim  10 , wherein said rolling bodies are made of a material selected from the group consisting of chromium steel, a martensite stainless steel and boron-nitride. 
     
     
       13. A rolling device according to claim  10 , wherein at least one organomolybdenum compound is present in the grease composition in an amount of from 0.5 to 5 wt. %. 
     
     
       14. A rolling device according to claim  10 , wherein the grease composition comprises 70 to 95 parts by weight of the carbonate compound and 5 to 30 parts by weight of the lithium soap.